Electronic ignition system

ABSTRACT

An electronic ignition system designed to replace the breaker points, cam, centrifugal and vacuum mechanisms, thus providing a fully electronic ignition system. Output pulses synchronized with engine speed are provided by an electromagnetic pickup connected with an amplifier and pulse shaper. These pulses trigger a monostable multivibrator which produces a variable-duration output pulse. The output pulse from this monostable multivibrator is coupled so that the termination thereof effects application of electrical energy to the sparkplugs of an internal combustion engine. The duration of the pulse from the monostable multivibrator is controlled through the utilization of an electronic spark-advance means which includes an electronic function generator. The function generator produces a waveform of predetermined shape which commences upon initiation of the spark (the termination of the signal from the controlled AND gate). The output of the function generator is applied to the timing circuit in the monostable multivibrator thereby to control the duration of the signal therefrom in a manner to provide the desired spark advance as engine speed increases. Also provided is a switch means for introducing additional spark advance in response to increase in vacuum in the manifold of an internal combustion engine.

United States Patent Polo 1 Dec. 2, 1975 ELECTRONIC IGNITION SYSTEM breaker points, cam, centrifugal and vacuum mecha- [76] Inventor, Benito Polo 9446 Borson St nisms, thus providing a fully electronic ignition sys- Downey, Calif. 90241 Output pulses synchronized with engine speed are [22] Flled' 1974 provided by an electromagnetic pickup connected [21] Appl. No.1 461,773 with an amplifier and pulse shaper. These pulses trigger a monostable multivibrator which produces a Apphcamm Data variable-duration output pulse. The output pulse from commuanon-m-part of 361,652, y 18, this monostable multivibrator is coupled so that the 1973, which is a continuation of Ser. No. 167,900,

Aug. 2, 1971.

[52] US. Cl. 123/148 E; 123/117 R [51] Int. Cl. F02P 5/04 [58] Field of Search 123/117 R, 148 E, 148 DC [56] References Cited UNITED STATES PATENTS 3,202,146 8/1965 Short 123/148 E 3,587,552 6/1971 Varaut 123/148 E 3,592,178 7/1971 Schiff 123/148 E 3,660,689 5/1972 Oishi 123/148 E 3,756,212 9/1973 Schirmer 123/148 E 3,800,757 4/1974 Finch 123/148 E 3,811,420 5/1974 Vogel 123/148 E Primary Examiner-Wendell E. Burns Assistant ExaminerRonald B. Cox

Attorney, Agent, or FirmNilsson, Robbins, Bissell, Dalgarn & Berliner termination thereof effects application of electrical energy to the sparkplugs of an internal combustion engine.

The duration of the pulse from the monostable multivibrator is controlled through the utilization of an electronic spark-advance means which includes an electronic function generator. The function generator produces a waveform of predetermined shape which commences upon initiation of the spark (the termination of the signal from the controlled AND gate). The output of the function generator is applied to the timing circuit in the monostable multivibrator thereby to control the duration of the signal therefrom in a manner to provide the desired spark advance as engine speed increases.

Also provided is a switch means for introducing additional spark advance in response to increase in vacuum in the manifold of an internal combustion engine.

[57] ABSTRACT An electronic ignition system designed to replace the 8 Claims, 7 Drawing Figures J8 /\5 /@O 68 $0 K547. 50720 flMPL/F/EB vflQ/Q/SLG mas/vs T/c PULSE CONTROLLED WVEETEE' 15317 629521? P/CK u tam/ 52. MO/VOSTQBLE BUFFER 46 MULWV/BE/QmlQ l MULT/V/BEATOR GEM/CONDUCTO/Zl 6W/TCH I "lL5cT/2oA//c l FUNCTION I GENERATOR, I CONTROL AMpL/F/E/e Q VQCUU/Vl 84 flDVAA/CE B/As 6W/7CH /O4 60 l /o@ *0.

/6A//7'/O sun-r014 68 2 US. Patent Dec. 2, 1975 Sheet 2 of4 3,923,029

Sheet 3 0f 4 US. Patent Dec. 2, 1975 U.S. Patent Dec. 2, 1975 Sheet 4 of4 3,923,029

OC) TPO T FIG.5C.

OUTPUT O ELECTRONIC IGNITION SYSTEM REFERENCE TO OTHER APPLICATIONS This application is a continuation-in-part of my co pending application Ser. No. 361,652, filed on May 18, 1973, which is a continuation of my application Ser. No. 167,900, filed on Aug. 2, 1971. i i

BACKGROUND OF THE INVENTION It has long been known that to provide maximum burning of the air-fuel mixture in the cylinder of an internal combustion engine, there must be provided an SUMMARY OF THE INVENTION An electronic ignition system wherein an electromagnetic synchronization device provides an output signal representative of engine speed. Such output signals are appropriate spark of sufiicient magnitude and duration.

The time required for complete combustion of the mixture is approximately one millisecond. It has also been known that to provide properly timed combustion thereby to properly transmit the power generated as a result of this combustion to the crankshaft, the initiation of the spark must be advanced as engine speed increases.

With prior art ignition systems utilizing traditional breaker points and condensers in conjunction with the battery and coil, various difficulties were encountered resulting in compromises as to coil design thereby to provide sufiicient voltage at high engine speeds without imparting damage to the remainder of the ignition system. Even so, at a relatively high engine spped, it was found that the air-fuel mixture introduced into the cylinder was only partially or improperly burned in many instances. As a result, undesirable pollutants were introduced into the atmosphere. Furthermore, it was found that the various mechanical components comprising a bulk of the ignition system were constantly in need of adjustment or replacement as a result of wear.

Furthermore, as above referred to, the spark timing advance mechanisms utilized to accomplish the advance of the spark at high engine speeds were also mechanical and took the form of camshaft springs and weights commonly referred to as a centrifugal spark timing advance mechanism and a pneumatic actuator commonly known as the vacuum spark timing advance mechanism. Again, these mechanisms introduced inaccuracies as well as difficulties in adjustment and maintenance.

In an attempt to solve some of the foregoing problems, various electronic ignition systems have been developed. Representative of such systems are those described in US. Pat. Nos. 3,202,146; 3,363,615; 3,368,539; 3,357,416; 3,434,462 and 3,587,552, all of which were cited in the above-referred-to applications. Although these electronic ignition systems solved some of the problems inherent in the mechanical systems heretofore used, difficulties remained. For example, in these systems, the traditional mechanical spark advance timing mechanisms utilizing the centrifugal and vacuum devices are retained in the system or have been replaced by other mechanical apparatus, thus injecting much of the prior art problems previously existing. In those instances where the mechanical apparatus has been eliminated, reliance is placed upon the ability of an electronic oscillator to detect the passage of a metal part which changes the Q of the resonant circuit to thereby detect the speed of the engine and provide an ignition advance signal.

These prior art systems leave much to be desired insofar as efficiently and completely burning all of the fuel injected into the cylinder during the entire operatapplied to a pulse generator to initiate the pulse having a variable duration, the duration being determined by the desired spark advance depending upon engine speed. The pulse is coupled to a semiconductor switch so that upon termination of the pulse, a spark is generated at a sparkplug to initiate combustion of the air-fuel mixture in the cylinder. Simultaneously with the termination of the signal from the pulse generator, an electronic function generator is triggered and is caused to provide an output which in turn is coupled to the pulse generator thereby to effect termination of the output pulse therefrom in a manner representative of the desired spark advance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating generally an electronic ignition system in accordance with the present invention;

FIG. 2 is a partly diagrammatic illustration of an electronic ignition system in accordance with the present invention;

FIG. 3 is a schematic circuit diagram of an electronic ignition system in accordance with the present invention;

FIG. 4 is a diagram illustrating waveforms taken at various points throughout the circuit of FIG. 3; and

FIGS. 5, 5A, 5B and 5C are schematic diagrams illustrating specific circuits utilized in the preferred embodiment of the present invention.

DESCRIPTION OF THE DETAILED EMBODIMENT As is illustrated in FIG. 1, an electronic ignition system in accordance with the present invention includes a first pulse generator 10 which is adapted to provide a series of output pulses having a predetermined and fixed amplitude and duration. The frequency of the pulses generated by the pulse generator 10 is representative of the engine speed of the internal combustion engine which is utilizing the electronic ignition system in accordance with the present invention. Thus, appearing on the lead 12 is a plurality of pulses 14 having a predetermined amplitude and duration and frequency (or repetition rate) representative of engine speed. The pulses 14 are applied as an input signal to a second pulse generator 16. The second pulse generator provides a plurality of output signals l8 appearing on the lead 20. Each of the output signals 18 has a leading edge 22 substantially coincident with the leading edge of the pulses 14. However, the trailing edge 24 of the pulses 18 is caused to occur at variable times. Thus, the output signal from the second pulse generator 16 constitutes a plurality of pulses of predetermined amplitude but variable duration. The occurence of the trailing edge 24 of the pulses 18 is determined by the electronic spark advance means 26. The electronic spark advance means 26 in response to the occurence of the trailing edge 24 of the pulses 18 produces an output signal which varies in a predetermined manner as a function of time. This output signal is applied by the lead 28 to the second pulse generator 16. Through the combination of the repetition rate of the pulses 14 and the particular function with respect to time of the signal applied from the electronic spark advance means 26 over the lead 28, the trailing edge 24 of the pulses 18 will be caused to occur in such a manner as to accommodate the required spark advance to effect efficient and complete combustion of the air-fuel mixture in the cylinders.

Simultaneously upon the occurence of the trailing edge 24 of the pulses 18, a semiconductor switch means 30 is caused to effect the sequence of events in the ignition 32 causing application of a spark to the combustion chamber in the cylinder.

Referring now more particularly to FIG. 2, the electronic ignition in accordance with the present invention isillustrated in some further detail. As is therein shown, the first pulse generator includes an iron disc 40 which is connected to the crankshaft 42 of the internal combustion engine and thus is rotated thereby. The disc 40 is notched as illustrated at 44, 46, 48 and 50. These notches are equiangularly disposed about the periphery of the disc 40 and represent the number of sparkplugs which will fire during each revolution of the disc. Thus, as is illustrated in FIG. 2, four sparkplugs will fire during each revolution of the disc 40 and such represents an eight-cylinder internal combustion engine. In the event the apparatus is applied to a six-cylinder internal combustion engine, there would be three such notches disposed 120 apart. Although the disc is shown as being notched, other configurations may be utilized as desired. That is, the notches may be replaced by protruding lobes, or a non-ferrous disc may be utilized with magnetic materials inserted at spaced positions thereabout. In any event, the notches, protrusions, or ferrous inserts cooperate with an electromagnetic pickup means 52 designed to sense the magnetic discontinuities in the disc and provide on the lead 54 an output signal which is applied to an amplifier and pulse shaper 56. The amplifier and pulse shaper 56 then produces the series of pulses 14 on the lead 12 as above described.

The second pulse generator 16 is a variable controlled AND gate 60 and inverter buffer 62. The output signal appearing on the lead is the pulses 18 as above described.

Also provided is a monostable multivibrator 64 which senses the trailing edge 24 of the pulses 18 and responsive thereto provides an output signal of predetermined duration and amplitude which in turn is applied to the power amplifier 66. The power amplifier 66 provides an output signal to control the semiconductor switch which in turn controls the generation of the spark as is well known.

The battery 68 is shown with one terminal 70 connected to a point of common reference such as ground 72 while the other terminal 74 is connected through the ignition switch 76 and ballast resistor 78 to one terminal 80 of the ignition coil 82. The other terminal 84 of the ignition coil 82 is connected to the semiconductor switch 30. The secondary coil 86 of the ignition coil 82 is connected through the distributor 88 and to the sparkplugs 90 by way of the various leads 92, which is well known in the art. Thus, after the ignition switch is closed, the battery current is continuously applied through the primary winding 81 of the ignition coil and through the semiconductor switch 30 which is normally closed thus causing the usual buildup of magnetic flux in the ignition coil 82. The signal from the multivibrator 64 causes the semiconductor switch 30 to open thus generating a high voltage signal in the secondary coil 86 of the ignition coil- 82 which generates the spark in the sparkplugs as is well known.

The output signal from the trailing edge monostable multivibrator 64 is also applied by way of the lead as a trigger signal to the function generator 102. The function generator is utilized to provide an output signal which is a predetermined function with respect to time. The function which is chosen is that which is desired for the particular spark advance profile as is requied for the particular internal combustion engine and the mode of operation thereof under consideration. The output of the function generator 102 is applied to a control amplifier 104, the output of which in turn is applied to the variable controlled AND gate .60. The output of the control amplifier is the function generator signal properly amplified for application to the AND gate 60, thereby to.determine the occurence of the trailing edge of the output signal therefrom. As above described, such in turn determines the occurence of the spark. Thus, by proper combination of the output signal from the function generator and the pulses from the first pulse amplifier 10, the desired spark advance can be obtained.

If desired, and to control those situations where the internal combustion engine is not under load, a vacuum advance bias switch as illustrated at 106 may be utilized. Such an apparatus senses the vacuum present in the intake manifold of the internal combustion engine and automatically injects a predetermined amount of bias at the control amplifier 104. Such bias effectively shifts the electronic function generated by the function generator 102 a predetermined amount to thus appropriately advance the spark.

Referring now more particularly to FIG. 3, there is illustrated in further detail an electronic ignition system constructed in accordance with the present invention. As is therein shown, the electromagnetic pickup 52 includes a coil 108 which is wound upon a core of ferromagnetic material 110 which is positioned adjacent the disc 40 which is rotated by the engine crankshaft. The coil 108 has one terminal 112 connected to bus 116 and the other terminal 114 connected to bus 118. A source of potential provided by the resistor 120, the capacitor 122 and the zener diode 124, is connected such that the positive terminal thereof is connected to the bus 116 and the negative terminal thereof is connected to the bus 118, the bus 118 also being connected to ground potential as is illustrated. In the power supply the zener diode 124 provides regulation while the capacitor 122 provides filtering and the resistor is a dropping resistor thus providing a potential of approximately five volts on the bus 116. A capacitor 126 is connected from the terminal 128 on the coil 108 to the base 130 of the transistor 132. Also connected to the base 130 is a resistor 134, the other side of which is connected to ground as illustrated. An additional resistor 136 is connected from the bus 116 to the base 130 of the transistor 132. A load resistor 138 is connected from the bus 116 to the collector 140 of the transistor 132 while the emitter 142 is connected through a resistor 144 to ground. The base 146 of a transistor 148 is connected to the collector 140 of the transistor 132. A load resistor 150 is connected from bus 116 to the collector 152 of the transistor 148 while the emitter 154 thereof is connected through the resistor 156 to ground as shown. An additional transistor 160 has its emitter 162 also connected to ground through the resistor 156, while the collector 164 thereof is connected to the bus 116. The base 166 of the transistor 160 is connected to a common point 168 between the reference diode 170 and the resistor 172, the series combination of which is connected between the bus 116 and 118.

As the disc 40 rotates and the notches 44 through 50 pass the pickup device, thereby changing the magnetic flux appearing therein, pulses are generated which are coupled through the capacitor 126 and resistor 134 to the base of the transistor 132. The transistor 132 is normally non-conducting and upon application of the signal generated by the magnetic pickup device thereto,

becomes conducting. The transistors 148 and 160 comprise a differential amplifier with the transistor 148 normally conducting and the transistor 160 normally non-conducting. When the transistor 132 becomes conducting, the voltage appearing at the collector electrode 140 thereof drops causing the transistor 148 to become non-conducting and the transistor 160 to become conducting. This condition will be maintained until the voltage appearing at the base 146 of the transistor 148 overcomes the bias appearing across the resistor 156 at which time the transistor 148 will again become conducting thereby cutting off the transistor 160. This change in the state of conduction of the transistor 148 produces at its collector electrode a positivegoing pulse of five volts and 100 microseconds duration. The combination of elements thus far described comprises the first pulse generator which includes the electromagnetic pickup and the amplifier and pulse shaper 52 and 56 as shown in FIG. 2.

The collector 152 of the transistor 148 is also connected by the lead 174 as an input to the inverting NAND gate 176. The function of the NAND gate 176 is merely that of isolation and inversion and any device capable of performing these functions may be utilized in place of the NAND gate 176. It has howe/ er been determined that this function is appropriately performed by the structure employed as a NAND gate and such is therefore chosen as being preferred in the present invention.

The output from the gate 176 is applied by way of the lead 178 to an input terminal 180 of an AND gate 182. The other terminal 184 of the AND gate 182 is .connected by way of the lead 186 to a common point 188 between the capacitor 190 and the resistor 192. The other side of the capacitor 190 is connected to the output terminal 194 of the AND gate 182. A variable resistor 196 is connected from the resistor 192 to the collector 198 of the transistor 200, the emitter 202 of which is connected through the resistor 204 to ground. The function of the resistor 200 will be described more in detail hereinbelow.

The AND gate 182 functions toproduce an output signal of constant amplitude but variable duration. Under quiescent operating conditions, that is when no signal appears at the lead 178, the tenninal 180 of the AND gate 182 is high and in this particular circuit application is at 5 volts. Under these circumstances if the terminal 184 exceeds a threshold voltage which in this particular circuit application is approximately l.7 volts, then the output terminal 194 is also high and in this particular application is at five volts. Upon application of the positive-going pulse to the lead 174 as above described, the output of the NAND gate 176 goes negative and drops from +5 volts to zero. Thus, zero volts is applied to terminal 1800f the AND gate 182. When such occurs, the AND gate output is caused to change states from high to low and thus drops from +5 volts to zero volts. When such occurs, the change in state is coupled to the input terminal 184 of the AND gate 182. Capacitor 190 immediately commences charging toward +5 volts through the resistors 192, 196 and 276 and to the bus 116. When the charge across the capacitor 190 exceeds the 1.7 volt threshold voltage, the output signal at the terminal 194 of the AND gate 182 will then again go to its high or +5 volt state. Such assumes of course that the voltage appearing at the terminal has again gone to the high or +5 volt state, which will have occurred at the termination of the input signal appearing on lead 174 connected to the NAND gate 176. This time duration as above pointed out is approximately lOO microseconds.

When the engine speed is relatively slow, that is approximately 0-600 revolutions per minute, the spark should occur substantially at top-dead center of the piston stroke and thus no spark advance is required. Under these circumstances, the time constant for charging the capacitor is such that the duration of the negative-going pulse at the output terminal 194 of the AND gate 1,82iimparts no spark advance. The variable resistor 196 provides appropriate adjustment to effect this time constant at the desired point.

The negative-going signal thus generated by the AND gate 182 is applied as an input signal to the inverting NAND gate 210. NAND gate 210 functions precisely the same as NAND gate 176 and thus provides a positive-going signal on the lead 212 having a duration as determined by the controlled AND gate 182. This signal is differentiated by the capacitor 214 and resistor 215 with a differentiated signal appearing at the input terminal 216 of the NAND gate 218. The NAND gate 218 functions as a monostable multivibrator responsive only to negative-going signals. Thus, by differentiation of the output pulse from gate 210, only the negativegoing spike caused by the trailing edge of the output pulse effects any response in the NAND gate 218. Thus, when the negative-going signal appears at the terminal 216 of the NAND gate 218 and drops below the threshold of 1.7 volts, the output appearing on the lead 220 of the NAND gate 218 is a positive-going signal. The input differentiating network of the AND gate 218 is designed such that the output signal has a duration of 100 microseconds. It should be noted that the leading edge of this output'signal coincides with the trailing edge of the output signal from the AND gate 182. This output signal is coupled through the inverting NAND gate 222 and appears as a negative-going signal 100 microseconds in duration on the lead 224. This signal is coupled by way of the resistor 226 to the base 228 of the transistor 230. The emitter 232 of the transistor is connected through the emitter resistor 234 to ground as illustrated and also by way of the lead 236 to the base 238 of the transistor 240, the emitter 242 of which is connected to ground as illustrated. The collectors 231 and 241 of the transistors 230 and 240 are each connected through the primary winding 81 of the ignition coil 82 and through the ballast resistor 78 and the ignition switch 76 to the battery 68. The resistors 244 are connected in series between the collectors of the two transistors and ground, and a diode 248 is connected between the common point of the two resistors and the lead 236. The combination of the two resistors 244 and 246 and the diode 248 functions to protect the transistors 230 and 240 from inductive kick voltage of high magnitude, for example, in excess of 200 volts. During quiescent conduction, that is when no signals are applied from the magnetic pickup through the circuit thus far described, the transistors 230 and 240 are in their 244 and 246 conducting states since the emitter-base diodes of each are forward biased as is well known to those skilled in the art. Under this circumstance those skilled in the art will recognize that the battery 68 potential is applied continuously through the primary winding 81 of the ignition coil 82 and through the conducting transistor 240 to ground. Thus, the magnetic flux is built up in the ignition coil. Upon application of the negative-going 100 microsecond signal by way of the lead 224 to the base of the transistor 230, the'transistors 230 and 240 are caused to go to their non-conducting state. As a result, current flow through the primary winding ceases and the magnetic field collapses. As a result thereof, the secondary coil has induced therein a high voltage potential which is applied as above described to the sparkplugs 90. Upon termination of the negative-going pulse to the transistor base 228 of the transistor 230, the transistors 230 and 240 again return to their conducting states and once again the current flows through the-primary winding 81 thus building the flux appearing therein to a maximum.

Turning now to the spark-advance circuit of the present invention, the output signal from the trailing edge monostable*multivibrator comprising the NAND gate 218 is applied through an inverting NAND gate 250 where it is inverted and at the lead 252 is a negativegoing 100 microsecond duration pulse. This pulse is applied to the cathode of the diode 254 the anode of which is connected through the capacitor 256 to ground. A common point 258 between the diode and the capacitor is connected to the base 260 of a transistor 262 which is connected in an emitter-follower configuration. The collector 264 thereof is connected to the bus 116 while the emitter 268 thereof is connected through the resistor 270 to ground. A resistor 272 is connected from the common point 258 to the bus 116.

It will be noted that the diode 254 is reversed biased by the output signal appearing on the lead 252 being high. Under these circumstances the transistor 262 is conducting. When the negative-going signal appears on the lead 252 at the output of the inverting NAND gate 250, the diode 254 is forward biased thus immediately shorting any charge which appears on the capacitor 256. Upon the expiration of the 100 microsecond pulse, the diode 254 is once again reversed biased and the capacitor 256 is connected in series with the resistor 272 between ground and the five volts appearing on the bus 116. As a result, the capacitor 256 will charge from its zero voltage condition toward five volts in the traditional charging cycle of a capacitor with a time constant determined by the resistor 272 and the capacitor 256. The charge appearing across the capacitor 256 is connected as the input signal to the base 260 of the transistor 262. since the transistor is in an emitter-follower stage, this output signal then appears across the resistor 270. The output signal is coupled by way of the resistor 274 to the base 206 of the transistor 200. The transistor 200 functions as an amplifier which inverts the signal appearing across the resistor 270 while at the same time amplifying the same. The output signal appears across the load resistor 276 connected between the collector 198 and the bus 116. Thus the signal ap pearing across the resistor 276 is applied to the resistors 192 and 196 which are connected to the capacitor thereby effectively decreasing the time constant required for the capacitor 190 to charge by an amount proportional to the signal appearing across the resistor 276. It will now be recognized that if the firing time for the sparkplugs occurs at any time during the change period of the capacitor 256, that is before it reaches its full charge, then this voltage is applied to the charge path of the capacitor 190 thereby decreasing its time constant for charging allowing it to reach the threshold of 1.7 volts faster than before. As a result, the trailing edge of the output signal from the controlled AND gate 182 occurs sooner. However, if the spark firing time occurs after the capacitor 256 has achieved substantially its entire charge, then the output signal developed by the transistor 200 will have no effect on the charge time of the capacitor 190 and thus the spark will not be advanced but rather will occur in the zero advance or retarded condition as will have been previously established by the adjustment of the resistor 196.

It will also be recognized by those skilled in the art that if the firing time occurs early in the charge cycle of the capacitor 256, then a substantial signal is applied by way of the transistor 200 to the charge circuit of the capacitor 190. Such substantially decreases the resistance appearing in the charge path and decreases the R-C time constant thus allowing the capacitor to more rapidly charge to a value above the threshold established for the controlled 'AND gate thereby terminating the output pulse therefrom much sooner. In this fashion the spark is advanced substantially and in direct relationship to the speed of the engine.

It will be noted that a switch 278 is connected between ground and a variable resistor 280 the other side of which is connected to the base 206 of the transistor 200. An additional resistor 282 is also connected between the base 206 and the collector 198 of the transistor 200. The switch 278 is connected to sense the vacuum appearing at the intake manifold of the engine. Upon the occurrence of a predetermined amount of vacuum at that point, for example, in the preferred embodiment approximately ten pounds per square inch, the switch 278 will close inserting the resistor 280 into the circuit and inserting it in parallel with the resistors 270 and 274, thus lowering the bias on the base of the transistor 200. As a result, the output signal at the collector of the transistor 200 increases thereby inserting an even greater amount of voltage in the charge path of the capacitor 190 causing it to reach the threshold voltage even sooner. As a result, upon actuation of the switch 278 the spark is advanced by a larger amount through the technique of effectively placing the function generated across the capacitor 256 on a pedestal of voltage.

Referring now to FIG. 4, various wave forms are illustrated taken at various points throughout the circuit of FIG. 3. In FIG..4, voltage is plotted on the ordinate and time along the abscissa. The curve 302 is taken across the resistor 134 and represents the signal generated by the electromagnetic pickup device. The curve 304 is taken from the collector 152 of the transistor 148 to ground and represents the input signal to the inverting NAND gate 176. The curve 306 is taken at the output of the inverting NAND gate .210. The curve 308 is taken from the collector 198 of the transistor 200 to ground and represents the voltage which is a wave function with respect to time that is applied to effectively reduce thetime constant in the charge path of 9 the capacitor 190. The curve 310 is the output signal of the inverting NAND gate 222 which is utilized to cut off the semiconductor switch consisting of transistor 240, and the curve 312 is the voltage applied to the sparkplugs 90.

In the left half of FIG. 4 the curves illustrated are taken during the time period when an internal combustion engine is operating at idle speed, that is in the range of approximately 600 revolutions per minute. Under these circumstances the electronic function generator produces a repetitive curve 308 and the spark occurs substantially at the conclusion thereof with the resultant of substantially no spark advance. It will be recognized that the curve 308 in the example given is substantially a logarithmic function and is generated by the charging of the capacitor 256 with that'function inverted through the amplifier including the transistor 200. It will be recalled that each time the spark is initiated the charge across capacitor 256 is shorted out, and the capacitor again commences to charge toward its maximum of 5 volts. Thus, the function 308 always commences at the same point. Thus, the points illustrated at 314 and 316 illustrate the commencement of the function each time the spark is initiated when the engine is at low speeds.

Referring now to the right half of FIG. 4 these curves are taken when the engine speed has substantially increased from idle. Again, it should be pointed out that the function curve 308 commences each time at the same point. Thus, the points 318, 320, 322 and 324 each illustrate the commencement of the function curve 308 as has above been described. It will also now be noted that the electromagnetic pickup generated curve 302 illustrates a substantially greater number of pulses per unit of time being generated. As each of these pulses is generated, the output signal from the controlled AND gate 60 also commences as is illustrated by the inverted waveform thereof at 306. However, it will be noted that the duration of the pulses on the right half of FIG. 4 at curve 306 are substantially shorter than those on the left half. Such occurs as a result of the effective decrease in resistance in the charge path of the capacitor 190 of the controlled AND gate 60, that is, from the function generator curve 308.-Thus as will be seen, during the time that the function generator curve is decreasing from the point 318 along its path 326, the charge across the capacitor 190 reaches the threshold voltage at a shorter period of time than is the case on the left half of FIG. 4 so that at the point 328, the controlled AND gate 60 changes states, thus causing the pulse in waveform 306 as illustrated at 330 to terminate, thereby shorting out the capacitor 256 and once again starting the function generator from its initial position as at 320, and also initiatingthe spark as shown in waveforms 310 and 312. The dashed lines show the function signal path if capacitor 190 were allowed to fully charge as was the case at the left half of of repetition of the pulses on the curve 306 will increase but the duration of each of the pulses will decrease as a result of the function generator output voltage being inserted sooner and thus closer to its point of commencement to effectively decrease the resistance in the charge path of the capacitor 190.

Although the function generated by the electronic function generator in the preferred embodiment thus far discussed is substantially logarithmic, it will be understood by those skilled in the art that the function may be any function of voltage with respect to time as may be desired for the particular engine application. As an example, a linear ramp may be generated through the utilization of an operating amplifier having a capacitor connected in afeedback relationship therewith, as is well known in the art. The ramp can be caused to terminate at any point during the timing function thus enabling an internal combustion engine to be operated during the relatively low speed such as at idle with zero spark advance and then inserting a spark advance as herein described at some predetermined point such as for example 600 revolutions per minute of engine speed and above.

Each of the NAND gates 176, 210, 222 and 250 as well as the trailing edge monostable device 218 may be constructed of circuits well known in the prior art. For example, a quadruple 2-input positive NAND gate, manufactured by Texas Instruments, Incorporated, of Dallas, Texas, circuit type SN7400 may be utilized. Such a circuit is illustrated in FIG. 5A for purposes of completeness of disclosure. It will be recognized by those skilled in the art that with the two emitters A and B connected together, as illustrated, when the input signal connected thereto goes from a low state to a high state in excess of a threshold voltage (greater than approximately 1.7 volts), the voltage appearing at the ter-- minal marked output goes from a high state to a low state. Likewise, if the input voltage applied to the interconnected emitters A and B is at a high state and then is driven below the threshold voltage, the output signal appearing at the terminal marked output will go from a low state to a high state and'will remain high until such a time as the signal appearing at the interconnected emitters again exceeds the threshold voltage at which time the output signal will return to its low state. Thus, by connecting the capacitor-resistor combination to the input terminals A and B interconnected together as is illustrated for the trailing edge monostable 218, and properly selecting the resistor and capacitor values to a desired time constant, one may obtain an output signal of constant duration and amplitude as hereinabove described.

By interconnecting two of the NAND gates as illustrated in FIG. 53, one may obtain the variable duration pulsewidth device 182 as hereinabove described. Thus, by connecting the capacitor between the output of the second NAND gate and the emitter B of the first NAND gate as illustrated and by connecting the emitter A of the first NAND gate to receive the output signal from the first pulse generator 10, the output voltage from the second NAND gate goes from a high to a low state when the input signal at emitter A goes from a high to a low state. The output remains low until the charge across the capacitor reaches the threshold level as above described at which time the output agains returns high.

If desired, one may utilize a commercially available AND gate also made by Texas Instruments, Incorpo-' rated, of Dallas, Texas, and referred to as the quadruple 2- input positive AND gate, for example circuit type SN5408. For purposes of completeness of disclosure, such a circuit is illustrated in FIG. SC, to which reference is hereby made. With the capacitor interconnected between the output terminal and the input terminal B and with the input terminal A connected to receive the input signal as previously described with respect to FIG. B, the desired output voltage waveforms will result.

It will be recognized by those skilled in the art that the appropriate connections to operating potential of five volts and to ground are made to each of the gates referred to in FIG. 3 as illustrated in FIG. 5.

SUMMARY OF SYSTEM OPERATION From the foregoing it can be seen that as the disc 40 is rotated by the engine crankshaft 42, a voltage signal is generated by the electromagnetic pickup 52 as each of the discontinuities pass by. This signal is then amplified by the amplifier pulse shaper 56.

The discontinuities in disc 40 are equally spaced at its periphery and the number thereof equal the number of sparkplugs fired per revolution of the engine. For example, in an eight-cylinder reciprocating internal combustion engine, four sparkplugs fire per revolution of the engines crankshaft. Consequently, in the specific disc 40, four slots or indentations spaced 90 of arc apart are required.

The electromagnetic pickup 52 is positioned perpendicular to the periphery of disc 40 and for an eight-cylinder engine at 45 before top-dead center or after topdead center with respect to the slots. Thus, the signal voltage pulse output from the first pulse generator occurs exactly 45 before top-dead center with respect to the particular cylinder to be provided with a spark for ignition.

This pulse then triggers the controlled AND gate 60 which is designed to generate a pulse ten milliseconds in duration at 600 RPM engine speed. Such occurs because the resistor 196 is effectively at ground and the function generator has little or no effect at this engine speed. This pulse, because of its time duration and the spark occurring on its termination, will retard the engine timing advance exactly 36 of engine crankshaft angle. When subtracted from the 45 setting of the electromagnetic pickup 52, there is provided a net of 9 before top-dead center basic timing advance for this engine (eight-cylinder) at 600 RPM.

Variable resistor 196 may be adjusted to add or subtract an additional 5 of engine crankshaft angle at 600 RPM thus providing an electronic means to further adjust the basic timing advance.

As the engine speed increases the function signal or control voltage 308 provided at the output of the control amplifier 200 becomes more positive and effectively shortens the duration of the pulse 306 from the controlled monostable 60. This, in effect, will advance the engines timing.

As the engine load decreases during cruise conditions and vacuum manifold pressure reaches l0 psi, the vacuum-actuated switch 278 closes connecting bias resistor 280 to ground which shifts control voltage 308 more positively. This shift causes a further reduction in the pulse duration of voltage output 306 at the controlled AND gate and an additional timing advance occurs. Variable bias resistor 280 may be adjusted to further provide means of control and to adjust the range of the vacuum-actuated timing advance.

The output voltage pulse 306 is applied to the trailing edge monostable 64 to generate a voltage 310. This voltage is then applied to the power amplifier 66 which connects the primary winding 81 of the ignition coil 82 to the semiconductor switch. Current flows at all times 12 through the primary 81 of the ignition coil 82 except at the time of the spark period voltage 312 which is microseconds, thus providing the sparkplugs with energy that is constant at all engine RPM.

There has thus been disclosed an electronic ignition system providing automatic electronic spark advance at desired engine speeds which eliminates problems inherent in the prior art systems.

What is claimed'is:

1. An electronic ignition system for internal combustion engines comprising:

A. electromagnetic means for generating a plurality of pulses,

I. said means generating one pulse for each spark plug which will fire during each revolution of a crankshaft in said engine, and

2. the repetition rate of said pulses being directly proportional to engine speed;

B. control means having first and second input terminals and an output terminal for providing a control signal having a duration variable with engine speed thereby to advance the firing of the spark plugs in said engine, said control signal upon termination thereof initiating the firing of a spark plug;

C. an electronic function generator means for automatically generating an electronic signal of predetermined but constant wave form having a characteristic matching the desired spark advance profile of said engine, said electronic signal commencing responsive to termination of said control signal;

D. means connecting said pulses from said electromagnetic means to said first terminal of said control means, said control signal being initiated by each of said pulses;

E. capacitive feedback means connected between said output terminal and said second input terminal for terminating said control signal a predetermined fixed time after initiation thereof in the absence of an electronic signal; and

F. means connecting said electronic signal to said second terminal for automatically advancing termination of said control signal as engine speed increases.

2. An electronic ignition system for internal combustion engines as defined in claim 1 wherein said control means includes a controlled AND gate the output signal of which changes from a first to a second state upon the application of a pulse to said first terminal, said output signal terminating when the charge on said capacitor reaches a predetermined point, the time of occurence of said point being determined by said electronic signal.

3. An electronic ignition system for internal combustion engines as defined in claim 1 wherein said function generator means includes capacitor means, means for initiating the charge cycle of said capacitor means substantially coincidental with initiation of the spark, and amplifier means coupled to receive as an input signal the charge on said capacitor means.

4. An electronic ignition system for internal combustion engines as defined in claim 3 wherein said amplifier means includes bias means, switch means connected to insert said bias means into said amplifier means, and means connecting said switch means to receive pressure signals from the intake manifold of said engine for actuating said switch means responsive to vacuum increase thereby advancing termination of said output signal.

13 5. An electronic ignition system for use with a direct current potential source and an ignition coil for applying electrical energy to sparkplugs to generate a spark for combustion of gases in an internal combustion engine comprising:

A. First pulse generator means for producing output pulses in timed relationship with said engine speed;

B. Second pulse generator means coupled to receive pulses from said first pulse generator means and responsive thereto to initiate production of output pulses having variable time duration and commencing with the commencement of said pulse from said first pulse generator;

C. Capacitive feedback means coupling said output pulses to the input of said second pulse generator means for terminating said output pulse a predetermined fixed time after initiation thereof, said time being determined by the charge time of said capacitor to reach a predetermined voltage level in the absence of other signals;

D. Semiconductor switch means for controlling application of said direct current to said ignition coil;

E. Means coupling the output signal of said second pulse generator means to said semiconductor switch means for initiating said spark upon termination of said second pulse generator output signal;

F. Electronic spark-advance means including:

1. electronic function generator means for providing an output signal which varies as a function of time, said variation corresponding to the desired spark advance profile of said engine;

2. initiating means connected for causing said function generator means to start to produce said output signal substantially coincidental with commencement of said spark; and

3. means coupling said output signal of said function generator to said second pulse generator means for terminating said variable duration pulse in a shorter time than without said function generator signal thereby to automatically advance commencement of said spark as said engine speed increases.

6. An electronic ignition system for internal combustion engines as defined in claim 5 wherein said electronic function generator means includes capacitor means, means for initiating the charge cycle of said capacitor means substantially coincidental with initiation of the spark, and amplifier means coupled to receive the charge on said capacitor means.

7. An electronic ignition system for internal combustion engines as defined in claim 6 wherein said coupling means includes monostable means responsive only to a the trailing edge of output pulses from said second pulse generator for providing pulses of constant duration and amplitude for controlling said semiconductor switch thereby to provide a constant spark at all engine speeds.

8. An electronic ignition system for internal combustion engines as defined in claim 7 wherein said initiating means includes means coupling said pulses of constant duration and magnitude to said capacitor means for initiating commencement of said capacitor means charge cycle.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,923,029

q DATED December 2, 1975 INVENTOR(S) Benito Polo It is certified that error appears in the ab0ve-identitied patent and that said Letters Patent are hereby corrected as shown below:

Q Column 6, Line 46 after "the" "AND" should be NAND- Columnv 6, Line 63 after "244" insert and 246-- Column 7, Line 6 'after "their" omit "244 and 246" q I d d Engnc an Scaled this ninth Day of March 1976 1 [SEAL] Arrest:

RUTH C. MASON c. MARSHALL DANN Alluring Officer (ommissimur ufParenrs and Trademarks 

1. An electronic ignition system for internal combustion engines comprising: A. electromagnetic means for generating a plurality of pulses,
 1. said means generating one pulse for each spark plug which will fire during each revolution of a crankshaft in said engine, and
 2. the repetition rate of said pulses being directly proportional to engine speed; B. control means having first and second input terminals and an output terminal for providing a control signal having a duration variable with engine speed thereby to advance the firing of the spark plugs in said engine, said control signal upon termination thereof initiating the firing of a spark plug; C. an electronic function generator means for automatically generating an electronic signal of predetermined but constant wave form having a characteristic matching the desired spark advance profile of said engine, said electronic signal commencing responsive to termination of said control signal; D. means connecting said pulses from said electromagnetic means to said first terminal of said control means, said control signal being initiated by each of said pulses; E. capacitive feedback means connected between said output terminal and said second input terminal for terminating said control signal a predetermined fixed time after initiation thereof in the absence of an electronic signal; and F. means connecting said electronic signal to said second terminal for automatically advancing termination of said control signal as engine speed increases.
 2. the repetition rate of said pulses being directly proportional to engine speed; B. control means having first and second input terminals and an output terminal for providing a control signal having a duration variable with engine speed thereby to advance the firing of the spark plugs in said engine, said control signal upon termination thereof initiating the firing of a spark plug; C. an electronic function generator means for automatically generating an electronic signal of predetermined but constant wave form having a characteristic matching the desired spark advance profile of said engine, said electronic signal commencing responsive to termination of said control signal; D. means connecting said pulses from said electromagnetic means to said first terminal of said control means, said control signal being initiated by each of said pulses; E. capacitive feedback means connected between said output terminal and said second input terminal for terminating said control signal a predetermined fixed time after initiation thereof in the absence of an electronic signal; and F. means connecting said electronic signal to said second terminal for automatically advancing termination of said control signal as engine speed increases.
 2. An electronic ignition system for internal combustion engines as defined in claim 1 wherein said control means includes a controlled AND gate the output signal of which changes from a first to a second state upon the application of a pulse to said first terminal, said output signal terminating when the charge on said capacitor reaches a predetermined point, the time of occurence of said point being determined by said electronic signal.
 2. initiating means connected for causing said function generator means to start to produce said output signal substantially coincidental with commencement of said spark; and
 3. An electronic ignition system for internal combustion engines as defined in claim 1 wherein said function generator means includes capacitor means, means for initiating the charge cycle of said capacitor means substantially coincidental with initiation of the spark, and amplifier means coupled to receive as an input signal the charge on said capacitor means.
 3. means coupling said output signal of said function generator to said second pulse generator means for terminating said variable duration pulse in a shorter time than without said function generator signal thereby to automatically advance commencement of said spark as said engine speed increases.
 4. An electronic ignition sysTem for internal combustion engines as defined in claim 3 wherein said amplifier means includes bias means, switch means connected to insert said bias means into said amplifier means, and means connecting said switch means to receive pressure signals from the intake manifold of said engine for actuating said switch means responsive to vacuum increase thereby advancing termination of said output signal.
 5. An electronic ignition system for use with a direct current potential source and an ignition coil for applying electrical energy to sparkplugs to generate a spark for combustion of gases in an internal combustion engine comprising: A. First pulse generator means for producing output pulses in timed relationship with said engine speed; B. Second pulse generator means coupled to receive pulses from said first pulse generator means and responsive thereto to initiate production of output pulses having variable time duration and commencing with the commencement of said pulse from said first pulse generator; C. Capacitive feedback means coupling said output pulses to the input of said second pulse generator means for terminating said output pulse a predetermined fixed time after initiation thereof, said time being determined by the charge time of said capacitor to reach a predetermined voltage level in the absence of other signals; D. Semiconductor switch means for controlling application of said direct current to said ignition coil; E. Means coupling the output signal of said second pulse generator means to said semiconductor switch means for initiating said spark upon termination of said second pulse generator output signal; F. Electronic spark-advance means including:
 6. An electronic ignition system for internal combustion engines as defined in claim 5 wherein said electronic function generator means includes capacitor means, means for initiating the charge cycle of said capacitor means substantially coincidental with initiation of the spark, and amplifier means coupled to receive the charge on said capacitor means.
 7. An electronic ignition system for internal combustion engines as defined in claim 6 wherein said coupling means includes monostable means responsive only to the trailing edge of output pulses from said second pulse generator for providing pulses of constant duration and amplitude for controlling said semiconductor switch thereby to provide a constant spark at all engine speeds.
 8. An electronic ignition system for internal combustion engines as defined in claim 7 wherein said initiating means includes means coupling said pulses of constant duration and magnitude to said capacitor means for initiating commencement of said capacitor means charge cycle. 